The Minnesota Vikings running back returned to practice Friday after taking a day off for a personal matter.

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The 2-year-old son of Minnesota Vikings running back Adrian Peterson has died after he was hospitalized with severe head injuries he sustained in an alleged assault, the Sioux Falls police department said in a statement.

Updated at 5:59 PM CDT on Friday, Oct 11, 2013

The 2-year-old son of Minnesota Vikings running back Adrian Peterson has died of severe head injuries he suffered in an alleged assault, Sioux Falls, S.D. police said Friday.

Police declined to identify the boy out of respect for his family and said it would release his name next week.

"Thank you to my family, my fans and fans of other teams for their support," Peterson tweeted soon after the police announcement. "The NFL is a fraternity of brothers, and I am thankful for the tweets, phone calls and text messages from my fellow players."

Earlier in the afternoon, before his son passed away, Peterson had said he was certain he would play Sunday, despite the serious personal matter that caused him to miss practice earlier this week.

Peterson had declined to speak Friday specifically about the situation, asking reporters to respect his and his family's privacy. His father, Nelson Peterson, had told local newspapers that one of Peterson's sons was in critical condition at a hospital in South Dakota.

The man accused in the case, Joseph Patterson, 27, is charged in Lincoln County with aggravated assault and aggravated battery on an infant. He had a court appearance Friday and was ordered held on $750,000 cash bond.

Jane Bammert, owner of the Little Coalinga Bar, confirmed to The Associated Press that Peterson stopped by the Sioux Falls restaurant Thursday for a turkey sandwich. He was not at practice that day for what the Vikings described only as a personal matter.

Peterson is second in the NFL with 421 yards rushing and first in the league with five touchdowns.